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Magnetic Effect of Electric Current
In 1820 Hans Christian Oersted during his experiment found that when an
electric current flows in a wire it moves a compass needle and this effect lasts as
long as the current flows through the wire. This experiment established the relation
between electricity and magnetism.
If we place a compass near to a electric current carrying wire we can observe a
deflection in compass needle. The needle of compass gets deflected by a magnetic
field produced by current carrying wire. This effect which produced by the flow of
electric current is called “Magnetic Effect” of electric current.
In this unit we will learn about Magnetism, Magnet, Magnetic effect of electric
current and its applications.
Magnetism:
The magnetism is the property possessed by certain bodies of attracting or
repelling other bodies of magnetic substances.
Magnet:
A magnet is an object or a device that gives off an external magnetic field.
Basically, it applies a force over a distance on other magnets, electrical currents,
beams of charge, circuits, or magnetic materials.The basic atomic structure of a
Magnet seems to align most of the molecules in the same direction. Since many
atoms have a magnetic moment (tiny magnetic field), all of the moments can add
up to create a magnet. Scientists use the word hysteresis to describe the way the
atoms stay aligned.
There are two types of magnets
Natural Magnet:
The magnet found in nature are called “natural magnets”
Artificial Magnet
The magnets which are made artificially are called Artificial Magnet.
On the basis of life of Magnetism the magnets can be classified into two categories
Permanent Magnet
The magnet which retains their magnetism for a long time is called permanent
magnet. The strongest and best permanent magnets are made of alloys like Almico
( Aluminium, Nickel, Cobalt and Iron); Permalloy (Cobalt, Nickel and Iron or Nickel
and Iron); Vicalloy (Cobalt, Iron and Vanadium).
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Magnetic Effect of Electric Current
Temporary Magnet
The magnets which retain their magnetism for a short time are called temporary
magnet. All electromagnets are temporary electromagnet because they show
magnetism till the flow of electric current when the flow of electric current stops the
magnetism ends in coil.
Magnetic Lines
It is possible to see this force through a simple
experiment:
Put a Bar Magnet under a sheet of glass and sprinkle
Iron Filings on the glass. The "lines of force" from the
Magnet show up clearly as the Filings form a pattern.
Notice that the attractive forces are greatest at the two
"ends" of the Magnet, where the majority of Filings
gather. We call these "ends" "poles."
The density of the pattern represents the strength of
the field, which is the magnitude of the force exerted Bar Magnet Experiment
upon a magnetic material placed at the point in the
field. These lines are called "lines of magnetic flux."
Magnetic flux: The total number of lines of force around a magnet is called
magnetic flux.
Types of Magnets
There are many different types of magnets. Permanent magnets never lose their
magnetism. There are materials in the world that are called ferromagnetic. Those
materials are able to create and hold a specific alignment of their atoms. Since
many atoms have a magnetic moment (tiny magnetic field), all of the moments
can add up to create a magnet. Scientists use the word hysteresis to describe the
way the atoms stay aligned.
Most of the magnets you see around you are man-made.
Since they weren't originally magnetic, they lose their
magnetic characteristics over time. Dropping them, for
example, weakens their magnetism; as does heating them,
or hammering on them, etc.
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Magnetic Effect of Electric Current
There are also air-core magnets. Air-core magnets are created by current flowing
through a wire. That current produces the magnetic field. You create an air-core
magnet by wrapping miles of wire around in a doughnut shape (toroid). When you
send current through the wire, a magnetic field is created inside of the doughnut.
Scientists sometimes use air-core magnets to study fusion reactions.
Electromagnets are different because they have a ferromagnetic material (usually
iron or steel) located inside of the coils of wire. The core isn't air; it is something
that aids in producing magnetic effects, so electromagnets are typically stronger
than a comparable air-core magnet. Air-core and electromagnets can be turned on
and off. They both depend on currents of electricity to give them magnetic
characteristics. Not only can they be turned on and off, but they can also be made
much stronger than ordinary magnets. You might see an electromagnet at work in
a junkyard lifting old cars off the ground
Magnetic Field
A magnetic field is defined as a region in which a magnetic force is present. In a
magnetic field, the magnetic dipole (two equal and oppositely charged or
magnetized poles separated by a distance) experiences a turning force, which tends
to align it parallel to the direction of the field. The concept of a magnetic field can
be understood with the help of the following activity:

Place a piece of cardboard over a magnet

Sprinkle some iron filings onto the cardboard

Tap the cardboard gently and draw what you see

The iron filings show the magnetic field of the magnet
Magnetic Effect:
The effect which applies a force over magnetic materials, beam of charges,
electrical current or on other magnet is called Magnetic effect.
Magnetic Lines of Force Due To Current in a Straight Wire
The direction of the magnetic field due to a current may be studied by drawing the
magnetic lines of force. A vertical wire AB is passed through a horizontal cardboard
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Magnetic Effect of Electric Current
PQRS. Ion filings are sprinkled on the cardboard. Current is passed through it by
connecting a battery to it. Iron filings spread evenly on the cardboard. When a
compass needle is placed on the cardboard, the direction of the needle will show
the direction of the magnetic field. The point on the cardboard where the north pole
of the needle is situated is marked. The needle is shifted a little so that its south
pole takes the same position where the north pole was situated previously. The
position of the north pole is marked. If the current is strong the lines will be
circular. The arrows on the circular lines show the direction of the magnetic field.
Magnetic Field Lines Due to Straight Wire
If the direction of the current is reversed, the lines will still be circular, but the
directions of the lines will be reversed, which can be verified using the compass
needle.
Electromagnets play an essential role in the operation of
Generators, Motors, Transformers, and Relays. Wrapping an
insulated Conductor Wire around an Iron object (i.e. large nail), and
then passing an electrical current through the Wire, construct
Electromagnets. The strength of the Electromagnet depends on
the number of "wraps", the size of the Wire, and the amount of
current flowing through the Wire.
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